| In recent years,China’s wind power technology has developed rapidly,and the scale of wind power generation has continued to expand.While achieving sustainable development,the grid connection of wind turbines has also brought new challenges to the stable operation of the power system.Factors such as mechanical power fluctuations or operating parameters changes of wind turbine may make certain wind turbines become oscillation sources,causing power oscillations in the wind farm and even in the entire power system.Finding the oscillation source in time is the prerequisite to ensure the safe operation of the wind farm and power system.Doubly-fed wind turbines are widely used in current wind farms because of its advantages.In this paper,based on the transient energy flow method,the location of the forced oscillation source in the doubly-fed wind farm is studied.Firstly,the basic structure of the doubly-fed wind turbine is introduced,the mathematical model of each part of the unit and the control strategy of the converter are established,and the simulation verification is performed on the PSCAD platform.Secondly,according to the calculation formula of the transient energy flow and the corresponding mathematical model,the transient energy flow for doubly-fed wind turbine is deduced and verified,and the energy flow power is defined as an index of energy flow direction.After adding the forced oscillation sources,the frequency characteristics of the DFIG grid-connected system are analyzed and verified by simulation.The simulation of adding an externally applied disturbance source in a single-machine infinity system is constructed,and the forced voltage source and forced current source are found by calculating the energy flow power.Then,the wind farm oscillation caused by the change of the operating parameters of the doubly-fed wind turbine is studied,the oscillation of each unit is analyzed,and the unit causing the oscillation is located by calculating the energy flow power.On this basis,the influencing factors of doubly-fed wind turbine oscillation energy are analyzed.Finally,the input-output structure of the doubly-fed wind turbine is analyzed,and the energy component expressions corresponding to the prime mover system and the excitation system of the doubly-fed wind turbine are derived.The control channel where the oscillation source is located is found out by using the transient energy flow method.The above research contents have been verified by corresponding simulations,and the results show that the research results of this paper can provide guidance for the research on the location of oscillation sources in wind farm. |
